Hydrocarbon sweep process

ABSTRACT

This invention relates to a process for freeing hydrocarbons, especially heavy or immobile hydrocarbons (such as undriven hydrocarbons, for example those of high viscosity and gravity), from underground formations. More particularly, this invention relates to a process for bringing to the earth&#39;&#39;s surface hydrocarbons trapped in an underground formation, as, for example, hydrocarbons remaining in the formation after primary recovery therefrom, and even after a water-flooding process has been accomplished in said formation, as a result of introduction into the formation of hot water at a point or points downstream from the producing well or wells.

United States Patent Terry et al.

[ 1 June 11, 1974 HYDROCARBON SWEEP PROCESS [75] Inventors: Ruel C.Terry, Morristown, N.J.;

John A. Sutherland, Houston, Tex.

[73] Assignee: Allied Chemical Corporation, New

York, NY.

[22] Filed: Sept. 7, 1971 [21] Appl. No.: 177,978

[52] US. Cl. 166/272 [51] Int. Cl E2lb 43/24 [58] Field of Search166/245, 272, 303

[56] References Cited UNITED STATES PATENTS 1,237,139 8/1917 Yeomans166/272 X 3,276,518 10/1966 Schlicht [66/272 3,332,485 7/1967 Colburn166/245 3,386,508 6/1968 Bielstein 166/272 3,500,915 3/1970 Fitzgerald166/272 Primary Examiner-Robert L. Wolfe Attorney, Agent, orFirm-Patrick L. Henry; Jonathan Plaut [57] ABSTRACT This inventionrelates to a process for freeing hydrocarbons, especially heavy orimmobile hydrocarbons (such as undriven hydrocarbons, for example thoseof high viscosity and gravity), from underground formations. Moreparticularly, this invention relates to a process for bringing to theearths surface hydrocarbons trapped in an underground formation, as, forexample, hydrocarbons remaining in the formation after primary recoverytherefrom, and even after a waterflooding process has been accomplishedin said formation, as a result of introduction into the formation of hotwater at a point or points downstream from the producing well or wells.

4 Claims, 3 Drawing Figures PATENTEDJUN 11 197.4 313 1567 FIG. 1 3

o o o o o o IY o o o o o o O O 0 FIG. 2

11- o o o o o o RUEL c. TERRY JOHN A; 'SUTHERLAND INVENTORS.

HYDROCARBON SWEEP PROCESS BRIEF DESCRIPTION OF THE PRIOR ART Theintroduction of heat into a formation is well known in the prior art asa means of lowering the viscosity of hydrocarbons found within theformation in order to bring them to the surface. Such processes includethe introduction of steam, as disclosed, for example, in US. Pat. No.2,412,765, and the introduction of hot water into the formation, asdisclosed, for example, in US. Pat. No. 3,465,826. Furthermore, it isknown in the prior art to introduce a heating medium to lower theviscosity of the'hydrocarbon found in the formation into one well and toremove the hydrocarbon from another well removed from the first, asdisclosed, for example, in US. Pat. No. 3,193,009.

However, none of the patents or processes of the prior art teach aprocess for treating wells in which primary recovery has beeneconomically concluded, taking advantage-of the paths opened by thatfirst recovery, and perhaps a water flood treatment, to continuouslyintroduce heat to the producing formation and produce hydrocarbons froma second point of exit updip (in the incline of the producing formation,closer to the surface) from the previously producing well.

It is to accomplish production of hydrocarbons in such situations asjust previously described that the processes of this invention have beendevised. The invention will become more apparent with relation to thefollowing description.

BRIEF DESCRIPTION OF THE INVENTION Generally, the invention relates to aprocess in which, preferably, hot water, or other hot liquid medium, isintroduced into a formation below the point of the previously or at thetime producing well. The formation is one in which at least primaryrecovery has occurred. That is, the first 25 percent, or whateverpercentage of hydrocarbons are freed from the well during the firstperiod of recovery, has taken place. Characteristically, production ofhydrocarbons'from the well has declined as the period of primaryrecoverycomes to an economic end. i

In some cases, the formation in which the well just disclosed has beenproducing has been water-flooded. That is, cold or ambient water hasbeen pumped through the formation in an attempt to increaseproductivity.

In any case, as a result of pimary recovery and/or water-flooding,channels of movement for the injected liquid and the hydrocarbons arefound in the formation.

According to the invention, hot water, i.e., water in the temperaturerange of 300 to 700F., for example, is pumped down into the formationthrough a well located below (i.e., downdip of) the producing well. At apoint updip of the producing well, even-hotter water is introduced intothe formation, such water being in the temperature range of 400 to 8 5QF., for example (higher temperatures required as you go deeper so thereis a differential between injection and producing temperature), but inany event at a temperature hotter than that introduced at the lowerpoint.

Hydrocarbons are removed at the point of production. Preferably a bleedwell is located below (i.e., downdip of) the lowest or first point ofintroduction to remove excess water, and maintain a constant injectionpressure.

According to the invention, the sweep of the hot water introduced at thefirst-mentioned well downdip of the producing well will be through thechannels already found in the formation toward the point of greater heatupdip therefrom. Heat introduced into the formation and the increasedpressure found in the formation as a result of entry of water thereinwill lower the viscosity of'the hydrocarbons and free them, thusallowing them to be floated along by the movement of the hot watertoward the point of egress. Since much of the hydrocarbon is disposedbetween individual sand particles in such formations, the movement ofthe water against each particle and the increased pressure, which causesa hydraulic gradient and fracturing, in addition to supplying thenecessary heat, will result in a freeing of a substantial part of thehydrocarbons still trapped in the formation, perhaps as much as percentor more in some cases.

Still generally, as applied to the usual formation, the hot water isinserted at injection points at the lowest (downdip) pointof productionin the formation theretofore. The next level of wells found updiptherefrom is then used as the producing wells, with wells still onefurther level updip being the points of hotest water injection, asdiscussed. Because of the channeling already found in the formation fromprimary recovery and water-flooding, if it has been performed, thehydrocarbons freed by the injection of the hot water, the increase inpressure in the formation and the sweep of the water, will move updiptoward the producing wells. When this series of producing wells iseconomically played out from its thus stimulated production, the processwill be continued updip, by using the just described producing wells asthe downdip injection wells, the wells of highest temperature as the newproducing wells and the next series of wells as the new wells of highesttemperature. Wells downdip may be used as excess pressure bleed wells.This process will thus continue progressing updip until the formationhas been completely swept.

Now that the invention has been discussed in general terms, it will bediscussed in more detail with reference to the following drawings.

FIG. 1 is a schematic showing ofthe invention with relation to anunderground formation and individual wells for injection of hot liquidinto the removal of liquids from the formation; and

FIGS. land 3 are embodiments showing the particular well pattern forapplying the invention.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, a typical formation isshown wherein the trapping fault occurs, say along line AA. The oil orgas producing zone B in the formation has been operated for primaryproduction previously through well 3, shown schematically. It isproposed to introduce downdip from the well 3 into a second well 4 hotwater in the ing well 3 is found a second hot water injection well 5,

the water introduced into well 5 being hotter than that 3 introducedinto well 4, say 400 to 850F., for example, once more depending onformation depth and conditrons.

The introduction of hot water into the formation at 4 and 5 results in aheating up of the formation and an increase in the pressure therein tolower the viscosity of the hydrocarbon to be produced and increase thepressure to free it from its immobile position so that greater amountswill flow up the producing well 3. Since the formation has alreadyundergone primary recovery, and possibly even water-flooding, throughchannels of movement already established through which the hot water andthe hydrocarbons will flow to the producing well 3.

A bleed well 6 may be introduced downdip from the two hot water sources(4), in order to remove excess water, if necessary. The increase ofpressure as a result of the introduction of the water in the formationmay also result in subsidiary, cracking of the formation, i.e., openingup further or clearing out of channels for greater hydrocarbon flow.Where pressures become too great, however, the bleed well 5 may be usedto reduce the pressure situation.

The normal application of this invention may best be seen with relationto the well patterns in the typical field shown in FIGS. 2 and 3.

During the period of primary recovery, wells would have first beendrilled typically at a higher depth in the formation B, and then atlower depths. Those lower depth wells are identified by I in FIG. 2 andare at a depth shown ml in FIG. 3. Further wells would have typicallybeen drilled, for example, at II, III and IV, moving across the fieldlaterally and updip. Primary hydrocarbon production would have occurredfrom such wells, with perhaps as much as 25 percent of the availablehydrocarbons in the field produced.

Typically, water-flooding of the field might then have been undertakento stimulate further recovery. Generally, the water would first beintroduced at the depth of the wells downdip, i.e., at the wellslabelled I, with pro- I, which are equivalent to the well 4 shown inFIG. 1. Hydrocarbons are produced through the producing wells at H,which are equivalent to the producing well in FIG. 1 indicated at 3. Hotwater is further introduced updip from the producing wells at II throughthe wells at III, which are equivalent to the injection well 5 inFIG. 1. The downdip bleed well or series of wells may again be included.Movement of the hot water from the I wells to the wells at III, theadded heat to lower the viscosity of the hydrocarbons in the formation,and the increased pressure in the formation result in a sweeping ofimmobile hydrocarbons out the producing wells at II.

It is contemplated that the introduction of the hot water and theremoval of the hydrocarbons will be simultaneous and continuous afterthe preliminary buildup period of hot water and therefore heating of theformation is accomplished. Rather than introduce the hot water at allthe wells of levels I and III and produce through all the wells at II,certain of the wells may be selected which from their. previousproduction histories would seem to be near the greatest areas ofimmobile hydrocarbons remaining in the formation. Furthermore, ofcourse, where the wells do not lie in the pattern shown in FIGS. 2 and3, additional well or wells may have to be dug in order to complete thedesired ering through the wells of III. In this way the whole fieldduction had through the wells updip from those first 1 wells and at thelevel of II. When the wells at II watered out, i.e., started producingsubstantially all water or at least hydrocarbons at an uneconomic rate,the same water-flooding technique would have been had with the injectionpoint being the wells at II and the production point of the wells updipat III. This technique of waterflooding would, perhaps, have been hadacross the whole field.

Applicants invention, as already discussed, involves the tapping of thefield after it has substantially undergone economic primary productionand, in some instances, water-flooding, and directing the hot water inthe formation in the manner previously described to stimulate furthereconomic recovery of hydrocarbons. The channels for movement of the hotwater and the hydrocarbons are also established in the formation. Thehydrocarbons that have not been removed are either of high viscosity orare otherwise rendered immobile within the formation. By introducing hotwater thereinto. The viscosity of the hydrocarbons is lowered, thepressure within the formation is raised, as discussed, and the sweepingmovement of the water all combine to free immobile hydrocarbons found inthe formation. I

Specifically, in the field diagramatically illustrated in FIG. 2, hotwater would be introduced into the wells at may be swept of asubstantial portion of its insitu hydrocarbons.

We claim:

1. Method for stimulating a hydrocarbon producing field having aplurality of separate wells including producing wells extending intodifferent areas of the field, comprising the steps of l injecting hotwater through at least one of said wells into an area downdip of atleast one producing well, (2) injecting relatively hotter water throughat least one of said wells into an area updip of said at least oneproducing well, (3) flowing said hot water from said first injectionarea toward said second substantially through channels in the formationalready existent as a result of earlier field production, (4) removinghydrocarbon from said at least one producing well, and repeating thesteps set forth above with the at least one of said wells updip of saidproducing well being the at least one producing well, said at least oneproducing well being the at least one of said wells downdip of saidlast-mentioned producing well for injection of hot. water, and injectingrelatively hotter into the field by at least one well further updip fromthe last-mentioned producing well.

2. A method as claimed in claim 1, further comprising removing waterfrom said formation downdip of said first-mentioned area of injection.

3. A method as claimed in claim 1, said water at said first area ofinjection being in the range of about 300 to about 700F.

4. A method as claimed in claim 3, said water at said second area ofinjection being in the range of about 400 to about 850F.

2. A method as claimed in claim 1, further comprising removing waterfrom said formation downdip of said first-mentioned area of injection.3. A method as claimed in claim 1, said water at said first area ofinjection being in the range of about 300* to about 700*F.
 4. A methodas claimed in claim 3, said water at said second area of injection beingin the range of about 400* to about 850*F.